// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_REGEXP_ARM64_REGEXP_MACRO_ASSEMBLER_ARM64_H_
#define V8_REGEXP_ARM64_REGEXP_MACRO_ASSEMBLER_ARM64_H_

#include "src/arm64/assembler-arm64.h"
#include "src/macro-assembler.h"
#include "src/regexp/regexp-macro-assembler.h"

namespace v8 {
namespace internal {

    class V8_EXPORT_PRIVATE RegExpMacroAssemblerARM64
        : public NativeRegExpMacroAssembler {
    public:
        RegExpMacroAssemblerARM64(Isolate* isolate, Zone* zone, Mode mode,
            int registers_to_save);
        virtual ~RegExpMacroAssemblerARM64();
        virtual void AbortedCodeGeneration() { masm_->AbortedCodeGeneration(); }
        virtual int stack_limit_slack();
        virtual void AdvanceCurrentPosition(int by);
        virtual void AdvanceRegister(int reg, int by);
        virtual void Backtrack();
        virtual void Bind(Label* label);
        virtual void CheckAtStart(Label* on_at_start);
        virtual void CheckCharacter(unsigned c, Label* on_equal);
        virtual void CheckCharacterAfterAnd(unsigned c,
            unsigned mask,
            Label* on_equal);
        virtual void CheckCharacterGT(uc16 limit, Label* on_greater);
        virtual void CheckCharacterLT(uc16 limit, Label* on_less);
        virtual void CheckCharacters(Vector<const uc16> str,
            int cp_offset,
            Label* on_failure,
            bool check_end_of_string);
        // A "greedy loop" is a loop that is both greedy and with a simple
        // body. It has a particularly simple implementation.
        virtual void CheckGreedyLoop(Label* on_tos_equals_current_position);
        virtual void CheckNotAtStart(int cp_offset, Label* on_not_at_start);
        virtual void CheckNotBackReference(int start_reg, bool read_backward,
            Label* on_no_match);
        virtual void CheckNotBackReferenceIgnoreCase(int start_reg,
            bool read_backward, bool unicode,
            Label* on_no_match);
        virtual void CheckNotCharacter(unsigned c, Label* on_not_equal);
        virtual void CheckNotCharacterAfterAnd(unsigned c,
            unsigned mask,
            Label* on_not_equal);
        virtual void CheckNotCharacterAfterMinusAnd(uc16 c,
            uc16 minus,
            uc16 mask,
            Label* on_not_equal);
        virtual void CheckCharacterInRange(uc16 from,
            uc16 to,
            Label* on_in_range);
        virtual void CheckCharacterNotInRange(uc16 from,
            uc16 to,
            Label* on_not_in_range);
        virtual void CheckBitInTable(Handle<ByteArray> table, Label* on_bit_set);

        // Checks whether the given offset from the current position is before
        // the end of the string.
        virtual void CheckPosition(int cp_offset, Label* on_outside_input);
        virtual bool CheckSpecialCharacterClass(uc16 type,
            Label* on_no_match);
        virtual void Fail();
        virtual Handle<HeapObject> GetCode(Handle<String> source);
        virtual void GoTo(Label* label);
        virtual void IfRegisterGE(int reg, int comparand, Label* if_ge);
        virtual void IfRegisterLT(int reg, int comparand, Label* if_lt);
        virtual void IfRegisterEqPos(int reg, Label* if_eq);
        virtual IrregexpImplementation Implementation();
        virtual void LoadCurrentCharacter(int cp_offset,
            Label* on_end_of_input,
            bool check_bounds = true,
            int characters = 1);
        virtual void PopCurrentPosition();
        virtual void PopRegister(int register_index);
        virtual void PushBacktrack(Label* label);
        virtual void PushCurrentPosition();
        virtual void PushRegister(int register_index,
            StackCheckFlag check_stack_limit);
        virtual void ReadCurrentPositionFromRegister(int reg);
        virtual void ReadStackPointerFromRegister(int reg);
        virtual void SetCurrentPositionFromEnd(int by);
        virtual void SetRegister(int register_index, int to);
        virtual bool Succeed();
        virtual void WriteCurrentPositionToRegister(int reg, int cp_offset);
        virtual void ClearRegisters(int reg_from, int reg_to);
        virtual void WriteStackPointerToRegister(int reg);

        // Called from RegExp if the stack-guard is triggered.
        // If the code object is relocated, the return address is fixed before
        // returning.
        // {raw_code} is an Address because this is called via ExternalReference.
        static int CheckStackGuardState(Address* return_address, Address raw_code,
            Address re_frame, int start_offset,
            const byte** input_start,
            const byte** input_end);

    private:
        // Above the frame pointer - Stored registers and stack passed parameters.
        // Callee-saved registers x19-x29, where x29 is the old frame pointer.
        static const int kCalleeSavedRegisters = 0;
        // Return address.
        // It is placed above the 11 callee-saved registers.
        static const int kReturnAddress = kCalleeSavedRegisters + 11 * kSystemPointerSize;
        // Stack parameter placed by caller.
        static const int kIsolate = kReturnAddress + kSystemPointerSize;

        // Below the frame pointer.
        // Register parameters stored by setup code.
        static const int kDirectCall = kCalleeSavedRegisters - kSystemPointerSize;
        static const int kStackBase = kDirectCall - kSystemPointerSize;
        static const int kOutputSize = kStackBase - kSystemPointerSize;
        static const int kInput = kOutputSize - kSystemPointerSize;
        // When adding local variables remember to push space for them in
        // the frame in GetCode.
        static const int kSuccessCounter = kInput - kSystemPointerSize;
        // First position register address on the stack. Following positions are
        // below it. A position is a 32 bit value.
        static const int kFirstRegisterOnStack = kSuccessCounter - kWRegSize;
        // A capture is a 64 bit value holding two position.
        static const int kFirstCaptureOnStack = kSuccessCounter - kXRegSize;

        // Initial size of code buffer.
        static const int kRegExpCodeSize = 1024;

        // When initializing registers to a non-position value we can unroll
        // the loop. Set the limit of registers to unroll.
        static const int kNumRegistersToUnroll = 16;

        // We are using x0 to x7 as a register cache. Each hardware register must
        // contain one capture, that is two 32 bit registers. We can cache at most
        // 16 registers.
        static const int kNumCachedRegisters = 16;

        // Load a number of characters at the given offset from the
        // current position, into the current-character register.
        void LoadCurrentCharacterUnchecked(int cp_offset, int character_count);

        // Check whether preemption has been requested.
        void CheckPreemption();

        // Check whether we are exceeding the stack limit on the backtrack stack.
        void CheckStackLimit();

        // Generate a call to CheckStackGuardState.
        void CallCheckStackGuardState(Register scratch);

        // Location of a 32 bit position register.
        MemOperand register_location(int register_index);

        // Location of a 64 bit capture, combining two position registers.
        MemOperand capture_location(int register_index, Register scratch);

        // Register holding the current input position as negative offset from
        // the end of the string.
        Register current_input_offset() { return w21; }

        // The register containing the current character after LoadCurrentCharacter.
        Register current_character() { return w22; }

        // Register holding address of the end of the input string.
        Register input_end() { return x25; }

        // Register holding address of the start of the input string.
        Register input_start() { return x26; }

        // Register holding the offset from the start of the string where we should
        // start matching.
        Register start_offset() { return w27; }

        // Pointer to the output array's first element.
        Register output_array() { return x28; }

        // Register holding the frame address. Local variables, parameters and
        // regexp registers are addressed relative to this.
        Register frame_pointer() { return fp; }

        // The register containing the backtrack stack top. Provides a meaningful
        // name to the register.
        Register backtrack_stackpointer() { return x23; }

        // Register holding pointer to the current code object.
        Register code_pointer() { return x20; }

        // Register holding the value used for clearing capture registers.
        Register string_start_minus_one() { return w24; }
        // The top 32 bit of this register is used to store this value
        // twice. This is used for clearing more than one register at a time.
        Register twice_non_position_value() { return x24; }

        // Byte size of chars in the string to match (decided by the Mode argument)
        int char_size() { return static_cast<int>(mode_); }

        // Equivalent to a conditional branch to the label, unless the label
        // is nullptr, in which case it is a conditional Backtrack.
        void BranchOrBacktrack(Condition condition, Label* to);

        // Compares reg against immmediate before calling BranchOrBacktrack.
        // It makes use of the Cbz and Cbnz instructions.
        void CompareAndBranchOrBacktrack(Register reg,
            int immediate,
            Condition condition,
            Label* to);

        inline void CallIf(Label* to, Condition condition);

        // Save and restore the link register on the stack in a way that
        // is GC-safe.
        inline void SaveLinkRegister();
        inline void RestoreLinkRegister();

        // Pushes the value of a register on the backtrack stack. Decrements the
        // stack pointer by a word size and stores the register's value there.
        inline void Push(Register source);

        // Pops a value from the backtrack stack. Reads the word at the stack pointer
        // and increments it by a word size.
        inline void Pop(Register target);

        // This state indicates where the register actually is.
        enum RegisterState {
            STACKED, // Resides in memory.
            CACHED_LSW, // Least Significant Word of a 64 bit hardware register.
            CACHED_MSW // Most Significant Word of a 64 bit hardware register.
        };

        RegisterState GetRegisterState(int register_index)
        {
            DCHECK_LE(0, register_index);
            if (register_index >= kNumCachedRegisters) {
                return STACKED;
            } else {
                if ((register_index % 2) == 0) {
                    return CACHED_LSW;
                } else {
                    return CACHED_MSW;
                }
            }
        }

        // Store helper that takes the state of the register into account.
        inline void StoreRegister(int register_index, Register source);

        // Returns a hardware W register that holds the value of the capture
        // register.
        //
        // This function will try to use an existing cache register (w0-w7) for the
        // result. Otherwise, it will load the value into maybe_result.
        //
        // If the returned register is anything other than maybe_result, calling code
        // must not write to it.
        inline Register GetRegister(int register_index, Register maybe_result);

        // Returns the harware register (x0-x7) holding the value of the capture
        // register.
        // This assumes that the state of the register is not STACKED.
        inline Register GetCachedRegister(int register_index);

        Isolate* isolate() const { return masm_->isolate(); }

        MacroAssembler* masm_;

        // Which mode to generate code for (LATIN1 or UC16).
        Mode mode_;

        // One greater than maximal register index actually used.
        int num_registers_;

        // Number of registers to output at the end (the saved registers
        // are always 0..num_saved_registers_-1)
        int num_saved_registers_;

        // Labels used internally.
        Label entry_label_;
        Label start_label_;
        Label success_label_;
        Label backtrack_label_;
        Label exit_label_;
        Label check_preempt_label_;
        Label stack_overflow_label_;
    };

} // namespace internal
} // namespace v8

#endif // V8_REGEXP_ARM64_REGEXP_MACRO_ASSEMBLER_ARM64_H_
